The remote detection of a gun that has just launched a projectile is of interest in both military and civil situations. Immediate and accurate location of a firing gun enables retaliatory action to remove the threat. It also makes feasible the deployment of protective systems. This is of great interest both in large conventional battlefield maneuvers and in the growing number of isolated sniper and ambush-type situations.
A literature survey of discussions of electromagnetic radiation from detonation of conventional explosives is contained in a report by Jonathon E. Fine and Stephen J. Vinci, “Causes of Electromagnetic Radiation from Detonation of Conventional Explosives: A Literature Survey”, Army Research Lab Adelphi, (December, 1998), also available at www.stormingmedia.us/cgi-bin/04/0479/A047953-83-1t.php. This report states that observers have detected radiation at frequencies as low as 0.5 Hz and up to as high as 2 GHz. Many investigators believe that the likeliest cause is charged particles created by ionization within the explosive region.
Although some modeling and observations have been reported, analysis has been crude and observations have been few. Detailed dependences of the radiation on the size of the explosive charge or with observation wavelength have not been determined. As a result, it is not clear what the optimum wavelengths are to use for observing the gun fire, or how distant the detection apparatus might be from the gun.